Tracing power to ecu

[89turboguy]

Hey guys, Im not one to bother you guys with what seems to be such a simple trace and find problem. I have read many of threads with similar issues to no avail. I could really use your help.

I have an 89 supra that i swapped a motor in from a 92. Got everything wired up, bolted up, and drove the car for a day putting on about 60 miles. On my way home at steady throttle around 65 mph the motor without warning shut down. It will turn over freely but will not fire.

I have come to the conclusion, that i have lost power to my fuel pump, and I think ECU. I am getting power to Ign Sw and +B1, but i am not getting power to Batt, +B, and M-Rel, as well as no check engine light.

I have and will continue to check fuses, relays, grounds, and connections, The main thing I am asking help with from you guys is Tracing the path of power from the battery to the ECU. I believe from all my reading that the lack of power to Batt, +B, and M-Rel pins means i am losing the 12v before the ECU, but please correct me if I am wrong. I cannot for the life of me read the TSRM wiring diagrams and could really use a simple description of where the power starts, stops, and passes through before reaching the ECU.

Any help is appreciated, cheers!

 

[NashMan]

cheak your efi fuse and corresponding relay

have fun

 

[89turboguy]

Thanks for the reply, I have checked the EFI fuse (good) and replaced the relay with a known working one, no change.

I have had enough fun with this car for a lifetime, lol.

I would also like to add that I am not getting power into the Diagnostics box at any pin. Tried jumping FP and +B1 when i found out there was no power there.

 

[3p141592654]

If you really don't have power at the EFI fuse which also powers BATT (and B+ through the EFI main relay) then you need to work backwards, and there isn't that much backwards to look at.

Check to see if you have blown fusible link AM2. This also powers the ignition circuit. Failing that all that is left is the battery fusible link (2.0L) and the alternator fusible link ALT. Since you say you have 12V at IGSW then those must still be good.

Also, there is no way you can have power at +B1, unless you also have power at +B, so please check that again.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=036

 

[89turboguy]

Great post, thank you.

You are correct about the +B1 and +B, there is no power to either.

EDIT, google answered my question on where to find those fusible links.

Let me give all this a shot and ill let you know what i find.

 

[3p141592654]

If its not the AM2 fusible link, then check that you have power to the junction box by honking the horn, checking the dome light works, or turning on the headlights. Better, yet, do that first then check AM2.

 

[89turboguy]

Alright, changed out AM2 and the ALT 100amp. Still not showing power. I am going to replace the battery fusible link (2.0L) tonight, though it doesnt really show signs of being blown. The horn, dome, and headlights do have power and work just fine.

 

[3p141592654]

Don't waste your time with the battery fusible link. The fact that you have power to the horn etc means it is okay.

 

[3p141592654]

You need to focus on junction box #2, because assuming your measurements are true, you have power going into the box at connector 2A pin2, and nothing coming out of conn 2F pin 5 (the batt circuit). The only thing in the path is AM2 and EFI fuse. Could also be bad connectors/pins etc, or the J/B itself.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=18
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=47

 

[89turboguy]

Alright PI, you are the man. I had a severed wire in the loom of JB2. All fixed and fired right up. Thank you, I owe you one.